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To burn a range of alcohols separately in air and measure the energy changes that take place.

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Introduction

Combustion of Alcohol Investigation Aim: To burn a range of alcohols separately in air and measure the energy changes that take place. Background Knowledge: Combustion is a chemical reaction between substances, usually including oxygen and usually accompanied by the generation of heat and light in the form of flame. The rate or speed at which the reactants combine is high, in part because of the nature of the chemical reaction itself and in part because more energy is generated than can escape into the surrounding medium, with the result that the temperature of the reactants is raised to accelerate the reaction even more Flames have a definable composition and a complex structure; they are said to be multiform and are capable of existing at quite low temperatures, as well as at extremely high temperatures. The emission of light in the flame results from the presence of excited particles and, usually, of charged atoms and molecules and of electrons. Combustion is one of the most important classes of chemical reaction, is often considered a climax phenomenon in the oxidation of certain types of substances. Although most flames have regions where reduction reactions are important, combustion is primarily the combining of combustible material with oxygen. The chemical processes in combustion are most commonly initiated by such factors as heat, light, and sparks. As the combustible materials achieve the ignition temperature specific to the materials and the ambient pressure, the combustion reaction begins. ...read more.

Middle

Mass (g) Initial Final Change Ethanol C2H5OH 46 0.99 200 21.5 31.3 9.8 Ethanol C2H5OH 46 1.01 200 21.5 30.2 8.7 Ethanol C2H5OH 46 1.02 200 22 33.5 11.5 Ethanol C2H5OH 46 1.02 200 22.5 33.1 10.6 Ethanol C2H5OH 46 0.99 200 22.3 34.3 12.0 Ethanol C2H5OH 46 0.99 200 21.6 32.8 11.2 Ethanol C2H5OH 46 1.01 200 20.5 30.8 10.3 Ethanol C2H5OH 46 1.02 200 22 31.8 9.8 Ethanol C2H5OH 46 1 200 22 31.1 9.1 Ethanol C2H5OH 46 1.03 200 23.25 31.5 8.2 Ethanol C2H5OH 46 1.02 200 22.5 30.9 8.4 Ethanol C2H5OH 46 0.99 200 22.9 33.4 10.5 Ethanol C2H5OH 46 0.99 200 22.5 32.6 10.1 Ethanol C2H5OH 46 0.99 200 23.5 34.4 10.9 Ethanol C2H5OH 46 1.01 200 21.5 32.8 11.3 Ethanol C2H5OH 46 1.01 200 21.5 34.0 12.5 Alcohol Water Temperature �C Name Formula RMM Mass (g) Mass (g) Initial Final Change Propanol C3H7OH 60 1 200 22 33.2 11.2 Propanol C3H7OH 60 1.02 200 21.75 32.7 10.9 Propanol C3H7OH 60 0.99 200 22.2 36.1 13.9 Propanol C3H7OH 60 1.02 200 22.5 34.3 11.8 Propanol C3H7OH 60 0.99 200 22.6 35.8 13.2 Propanol C3H7OH 60 0.98 200 21.6 34.0 12.4 Propanol C3H7OH 60 1.01 200 20.75 32.8 12.0 Propanol C3H7OH 60 1.01 200 22.5 33.8 11.3 Propanol C3H7OH 60 1.01 200 22 32.6 10.6 Propanol C3H7OH 60 1.01 200 23 34.9 11.9 Propanol C3H7OH 60 1 200 21.8 34.1 12.3 Propanol C3H7OH 60 0.98 200 22.5 33.9 11.4 Propanol C3H7OH 60 1.01 200 22.75 34.2 ...read more.

Conclusion

Also The fact that at higher temperatures, heat is lost faster to the air and out of the beaker, due to the bigger heat difference, making the higher temperatures more inaccurate, and making a shallower gradient on the graph. These factors could be avoided when repeating this experiment by using an advanced technique such as a bomb calorimeter. This is the most accurate way of measuring bond energies and this will be as accurate as we can get in our results. A diagram of a bomb calorimeter is shown below. Another factor, which could have effected our results, was incomplete combustion. This is when there is a limited supply of oxygen to carry out the reaction. This was shown by the fact that the alcohol was burning with an orange flame rather than blue. Some of the alcohol did not burn completely, carbon monoxide rather than carbon dioxide. If the oxygen supply is very limited then you get some atoms of carbon released before they can bond with any oxygen atoms. A carbon deposit (soot) on the bottom of the calorimeter indicated this. Since heat is given out when bonds form, less energy is given out by incomplete combustion. This would effect my results. I could overcome this problem by making sure that there is a good supply of oxygen for the reaction. For example using the bomb calorimeter pictured above. This would reduce incomplete combustion because air is pumped into it giving a good supply of oxygen. ...read more.

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